1. Field of the Invention
The present invention relates to a sheet post-processing apparatus, an image forming apparatus, and an image forming system including the sheet post-processing apparatus and the image forming apparatus.
2. Description of the Related Art
A sheet post-processing apparatus is widely used for performing post-processing, such as sorting, stapling, or stacking of sheets (printing sheets) received from an image forming apparatus, such as a copy machine or a printer. The sheet post-processing apparatus is, for example, a sorter or a finisher. The sheet post-processing apparatus is arranged downstream of the image forming apparatus.
For example, in Japanese Patent Application Laid-open No. H11-139673, a technology of such a sheet post-processing apparatus are disclosed in which a plurality of sheets conveyed to a staple tray in the sheet post-processing apparatus is aligned in a conveying direction by putting an edge of each of the sheets in contact with a rear-end fence arranged on a lower portion of the staple tray, and a discharging claw then directly scoops up the pile by supporting an edge of a pile of the sheets, thereby discharging the pile out of the staple tray.
In the conventional technology disclosed in Japanese Patent Application Laid-open No. H11-139673, a linear speed of the discharging claw when the discharging claw is moved into contact with the rear edge of the pile of the sheets is made different from a linear speed of the discharging claw when the rear edge of the pile is moved apart from the discharging claw, thereby preventing the sheets from being damaged by the discharging claw when the pile is discharged.
In the conventional technology, every time when the pile of the sheets is discharged from the staple tray, the discharging operation is controlled in the same control pattern. However, a load applied to the discharging claw during operation of discharging the pile depends on various conditions, such as a size and a type of the sheet, and the number of stapled sheets in the pile.
Therefore, if the discharging operation is always controlled in the same control pattern, it is difficult to improve a productivity of a high-speed machine in which a high accuracy and a high productivity are required.